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25 Cards in this Set

  • Front
  • Back

Skeletal muscle

-Large (up to 20cm), striated cells (banding pattern)

- multinucleated

- voluntary motor control

Cardiac muscle

- small, branched, striated cells

- intercalated disk, gap junctions

- single nucleus

Smooth muscle

-small cells with no striations

-single nucleus

Thick filaments

bundle of myosin proteins anchored in place by titian fibers

Thin filaments

bundle of actin proteins (structural backbone) anchored to z-lines


arrangement of characteristic proteins


area of adjacent sarcomeres with only thin filaments


area of sarcomere with thick filaments


middle of sarcomere, only find thick filaments, no overlap


helps anchor and hold thick filaments in place

-returns muscle to resting length after contraction (like a spring)

Sliding filament theory

myosin head binds to actin, and slides it, pulling z-lines closer together, and reducing the width of the I-bands

Molecular basis of contraction:

energized resting state --> cross-bridge formation --> power stroke --> rigor state --> back to resting state

muscle fatigue

the inability to generate or maintain muscle contraction

temporal summation

the increase in muscle tension from successive action potentials

unfused tetanus

partial dissipation of tension between subsequent stimuli

Fused tetanus

no time for dissipation of tension between rapidly recurring stimuli

Series elastic elements

titin, connective tissues, tendons.

'absord' tension and must be overcome to shorten the muscle

Isometric contraction

muscle has not shortened. Sarcomeres shorten, generating force, but elastic elements stretch, allowing muscle length to remain the same

Isotonic contraction

Sarcomeres shorten more but, because elastic elements are already shortened, the entire muscle must shorten

Optimal length sarcomere

lots of actin-myosin overlap and plenty of room to slide

short sarcomere

actin filaments lack room to slide, so little tension can be developed

long sarcomere

actin and myosin do not overlap much, so little tension can be developed

Motor unit recruitment

the activation of additional motor units

- the strength of muscle contraction depends on the number of motor units that are stimulated

motor unit

consists of a motor neuron and all the muscle fibers it controls

Muscular dystrophy

genetic diseases that result in the progressivedegeneration of skeletal and cardiac muscle fibers